The EAC91 is a miniature diode triode. The diode is a separate valve to the triode and can be operated in a separate circuit.
Mullard describe this valve as intended for service as an oscillator triode for use as a frequency changer (mixer). The sample circuit given by Mullard uses the diode as the non linear mixer element and rates the design as suitable for UHF use up to 300 MHz.
The triode with copper grid supports.
The diode is on the left. The mica discs top and bottom look to be double and thus conferring vibration resistance.
The thin glass tube envelope is 18 mm in diameter and, excluding the B7G base pins, is 47 mm tall.
References: Data-sheet & 1040. Type EAC91 was first introduced in 1947. See also1947 adverts.
